ECM_22343520_v1_Geotechnical Investigation · 132000.200173.1

                                            PROPOSED RENOVATIONS
                                            2 ARAKOON CRESCENT, SUNSHINE BEACH

            4.2         Topography
            During the site walk-over, topographic features specific to the site were noted, and ground slopes were
            recorded using a hand-held clinometer. As illustrated in a detailed survey by Minestaff Survey (Ref. M4371-
            3000-002, Rev A, dated 5 January 2023) in Text Figure 6 below, the existing residence is located on
            relatively gently sloping ground above the crest of the easterly facing high sand dune slope. The eastern
            property boundary extends partway down the dune slope.

                                                  Subject Site




            Text Figure 6: Detailed survey of the site and high dune, courtesy of Minestaff Survey

            Locally, Arakoon Crescent and The Esplanade may have been constructed by cut and fill earthworks. It is
            not known if the original roadworks fill is now retained along the western boundary, or if it was removed by
            excavations during residential construction. The natural surface profile at the site had been interrupted by
            historic landscaping and residential construction. Based on a visual assessment it appeared that cut and fill
            earthworks in the order of about 3 m deep and 1.5 m high had been previously undertaken, most of which
            were supported by retaining walls. An offset of about 5 m was present between the eastern edge of the
            existing residence, and the main break in slope to the high dune face.
            The dune face sloped at around 32° to 35° just off the crest, reducing to around 30° across the majority of
            the face. Beyond the eastern boundary a swale feature was apparent comprising a gently sloping bench
            (<5°) for a horizontal distance of about 5 m to 8 m (increasing in width progressing southwards) and a
            downslope mound estimated to be about 1.5 m high along the seaward edge. This mound had a backslope
            of about 25° (west towards the bench), with the seaward facing flank dipping at about 30°. It was unclear
            what created the swale feature in the central part of the dune face; however, it was likely due to previous
            earthworks, presumably to make an access track. Beyond the toe of the foredune a gently undulating
            incipient dune continued eastwards towards the main beach.

            Excluding the swale feature, the face of the dune was generally consistent and linear, steepening to about
            40° around 3 m up (vertically) from the toe. Beyond the toe of the main high dune, a trough was present of
            about 10 m width; then a small foredune around 1.5 m height, with side slopes of around 15° to 20°. A
            shorter trough of about 5 m width was then present to an incipient dune, around 1 m high; with side slopes of



             24 February 2023
             Report No. 22484-001-Rev0                                  6
Document Set ID: 22343520
Version: 1, Version Date: 16/03/2023